As is known in the art, antenna elements or radiators used in phased array antennas typically have good bandwidth or good cross-polarization isolation, but not both. For example, with proper design, an array of dipole elements can have very good cross-polarization isolation characteristics in all scan planes; however, bandwidth is limited. On the other hand, array antennas provided from notch radiators or Vivaldi radiators have excellent bandwidth, but relatively poor cross-polarization isolation off the principal axes.
Droopy bowtie elements disposed above a ground plane are a well known means for producing nominally circular polarized (CP) reception or transmission radiation patterns at frequencies from VHF to microwave wavelengths. Droopy bowtie elements are often coupled to a balun which is realized in a co-axial configuration involving separate subassemblies for achieving balun matching and arm phasing functions. Such a configuration typically results in an integrated antenna-balun assembly having good bandwidth but a poor cross-polarization isolation characteristic. Furthermore, such a configuration is relatively difficult to assemble.
It would, therefore, be desirable to provide an antenna and balun combination which results in an integrated balun-antenna element having both good bandwidth characteristics and good cross-polarization isolation characteristics.